In 2002, the mobile phone service of the 3G system, called the third generation in Japan, started. At first, small-size packets were used for transmission or reception to perform voice calls and mail transmission. However, with the introduction of high-speed downlink packet access (HSDPA), it became possible to transmit and receive larger-size packets for downloading of music files or streaming of video. With such an increase of packet capacities, the service of long term evolution (LTE) in which orthogonal frequency division multiple access (OFDMA) is used on the downlink also started for the expansion on the side of the wireless network. In addition, the launch of 4G service is scheduled to be made in around 2015. Accordingly, up to one gigabit per second (Gbps) will be achieved in a semi-fixed environment and up to 100 Mbps will be achieved even in a mobile environment.
With the increase in traffic as described above, the congestion of traffic is expected to be prevented by arranging a small base station that is inexpensive and easy to install. Various techniques for preventing the congestion of traffic are developed.
In one example, Non-Patent Literature 1 (especially, “5.2.2 Load Management”) discloses the exchange of traffic load information between eNBs such that the eNBs can control a traffic load appropriately. In one example, Non-Patent Literature 2 discloses the load balancing (e.g. change in handover parameters) based on the load information exchanged between eNBs.